Insects / Diseases / Invasives / Miscellaneous / Forest Pest Coop
Diseases occur on many of the root systems and woody tissues of Texas trees.
A list of common tree diseases is available below. However, there is rarely one factor leading to the decline or death of a tree. Many factors can make trees more susceptible to diseases. These include: heat, drought, flooding, lightning, animal damage, construction damage, soil compaction, wildfire, among others. Often the best way to prevent tree diseases or help trees recover is to keep trees healthy. Urban foresters and certified arborists receive training to care for individual trees. Resource or district foresters and consulting foresters receive training on improving the health of stand of trees or a forest.
Oak Wilt
This disease is responsible for the deaths of hundreds of thousands of oaks across 73 counties in Central and West Texas. All oaks are susceptible. An infection center starts when a sap feedling beetle visits a red oak that has died of the disease and feeds on the fungal spore mats that oak wilt creates. The beetle, now covered with spores, flies off, somtimes long distances, seeking a new would on a tree for its next meal thus infecting a new tree. Once established in a tree, the disease can also spread to other trees by root connections or root graphts moving from one tree to the next. For detailed information on the spread and control of oak wilt, go to http://www.texasoakwilt.org and click on the informational links below.
Hypoxylon Canker
This canker disease occurs in trees when they are stressed by environmental extremes and other damaging agents. As the tree declines, Hypoxylon secondarily colonizes the wood just under the bark causing a distinctive necrotic lesion and spore mat. The signs of the fungus appear as small patches but will eventually merge to form large strips along the trunk and limbs of the tree.
Root Rots
These rots are caused by decay fungi and water molds that kill woody trunk and root tissues and fine, feeder roots of trees. Some of the structural root rots include Armillaria spp., Ganoderma spp., and Heterobasidion annosum. Some of the feeder root rots include Phytophera spp. and Phymatotrichum omnivorum. Infection by root rots is often associated with previous wounding by animals, fire, lightning, and machines. However, they are very common in trees that are over-watered.
Bacterial Leaf Scorch
The bacterium Xylella fastidious causes a scorch to the leaf margins of many trees. Symptoms usually occur in early summar as plants come under heat stress. The bacteria lives in the water conducting xylem of the tree. It is transmitted by insects that feed on xylem fluid such as leafhoppers, sharpshooters and spittlebugs. It causes a stress-related decline resulting in stunting, brach die-back and death. The scorch on the leaves can be diagnosed by a chlorotic, yellow halo between the green and scorched tissue of the leaf, but it can can be mis-diagnosed as oak wilt in red oaks.
Further Information
Information on several tree diseases is available to print or download as a Forest Management Information Sheet.
For a comprehensive look at Plant Diseases in Texas go to: http://plantdiseasehandbook.tamu.edu/texlab/index.htm